Fans are a relatively low reliability component in a power supply system. Failure of one or more fans in a fan array may cause an entire power supply system to fail due to overheating. Conventionally, fans are often replaced at regular maintenance intervals to avoid fan failure, sometimes replacing good fans and increasing maintenance costs while failing to replace fans that fail at a rate higher than expected.
In highly available system, an ability to hot-swap and cold-swap failed field replaceable units (FRUs) is common and useful. However, a maintenance schedule that depends on waiting until a FRU fails subjects a user to down-time and possible damage upon occurrence of a random failure event. Accordingly, many systems use hot-swap FRUs, enabling the system to continue to run during failure and repair. However, many or most fan failures occur due to wearing or aging and, although a first failing fan may be replaced, other redundant fans are also likely to be near end-of-life.